Java generic signature is missing in forwarders containing value classes

[hamzaremmal]

Compiler version

ce57b71

Minimized code

final class Box[A](value: A) extends AnyVal

trait Foo:
  def foo[A](a: A): Box[A] = Box(a)

object bar extends Foo

Output

//> javap bar\$
Compiled from "test.scala"
public final class bar$ implements Foo,java.io.Serializable {
  public static final bar$ MODULE$;
  public static {};
  public java.lang.Object foo(java.lang.Object);
}

Expectation

//> javap bar\$
Compiled from "test.scala"
public final class bar$ implements Foo,java.io.Serializable {
  public static final bar$ MODULE$;
  public static {};
  public <A> A foo(A);
}

Notes

• The static forwarder has a (correct?) generic signature:

//> javap bar  
Compiled from "test.scala"
public final class bar {
  public static <A> java.lang.Object foo(A);
}

• The issue arise because the comparaison here fails with (a: Object): ErasedValueType(Box, Object) =:= (a: Object): Object.
  

  scala3/compiler/src/dotty/tools/dotc/transform/Mixin.scala

  Line 334 in ce57b71

  if TypeErasure.transformInfo(target, infoBeforeErasure) =:= sym.info then